Calcification in dermal fibroblasts from a patient with GGCX syndrome accompanied by upregulation of osteogenic molecules.
Calcification in dermal fibroblasts from a patient with GGCX syndrome accompanied by upregulation of osteogenic molecules.
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DOI：
10.1371/journal.pone.0177375
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发表时间：
2017
期刊：
影响因子：
3.7
通讯作者：
Utani A
中科院分区：
文献类型：
--
作者：
Okubo Y;Masuyama R;Iwanaga A;Koike Y;Kuwatsuka Y;Ogi T;Yamamoto Y;Endo Y;Tamura H;Utani A
γ-谷氨酰羧化酶（GGCX）基因突变导致GGCX综合征（OMIM：137167），其特征为弹性假黄瘤（PXE）样症状和凝血功能障碍。在这里，我们提出了一个55岁的男性与一个新的纯合缺失突变，c.2，221 delT，p.S741LfsX100，在GGCX基因。组织学检查显示弹性纤维和血管壁中有钙沉积，真皮中层有胶原沉积。对患者皮肤成纤维细胞（GGCX皮肤成纤维细胞）的研究表明，突变的GGCX蛋白更大，但其表达水平和细胞内分布与野生型GGCX蛋白无区别。免疫染色和酶联免疫吸附试验显示，羧基化不足的基质γ-羧基谷氨酸蛋白（ucMGP），GGCX的代表性底物和有效的钙化抑制剂，表明突变的GGCX是酶无活性的增加。在成骨条件下，钙沉积只在GGCX真皮成纤维细胞中观察到。此外，GGCX真皮成纤维细胞培养物中碱性磷酸酶（ALP）阳性细胞分别是正常真皮成纤维细胞培养物（n = 3）的23倍和7.7倍，无成骨诱导。成骨诱导后，GGCX真皮成纤维细胞ALP的表达和活性均高于正常真皮成纤维细胞。其他成骨标志物的mRNA水平在GGCX真皮成纤维细胞中也高于正常真皮成纤维细胞，包括骨形态发生蛋白6、侏儒相关转录因子2和无成骨诱导的骨膜蛋白（POSTIN）;以及Osterix、I型胶原α 2和有成骨诱导的POSTIN。总之，这些数据表明GGCX真皮成纤维细胞转分化为成骨谱系。这项研究提出了GGCX综合征患者异常钙化的另一种机制。
Gamma-glutamyl carboxylase (GGCX) gene mutation causes GGCX syndrome (OMIM: 137167), which is characterized by pseudoxanthoma elasticum (PXE)-like symptoms and coagulation impairment. Here, we present a 55-year-old male with a novel homozygous deletion mutation, c.2,221delT, p.S741LfsX100, in the GGCX gene. Histopathological examination revealed calcium deposits in elastic fibers and vessel walls, and collagen accumulation in the mid-dermis. Studies of dermal fibroblasts from the patient (GGCX dermal fibroblasts) demonstrated that the mutated GGCX protein was larger, but its expression level and intracellular distribution were indistinguishable from those of the wild-type GGCX protein. Immunostaining and an enzyme-linked immunosorbent assay showed an increase in undercarboxylated matrix gamma-carboxyglutamic acid protein (ucMGP), a representative substrate of GGCX and a potent calcification inhibitor, indicating that mutated GGCX was enzymatically inactive. Under osteogenic conditions, calcium deposition was exclusively observed in GGCX dermal fibroblasts. Furthermore, GGCX dermal fibroblast cultures contained 23- and 7.7-fold more alkaline phosphatase (ALP)-positive cells than normal dermal fibroblast cultures (n = 3), without and with osteogenic induction, respectively. Expression and activity of ALP were higher in GGCX dermal fibroblasts than in normal dermal fibroblasts upon osteogenic induction. mRNA levels of other osteogenic markers were also higher in GGCX dermal fibroblasts than in normal dermal fibroblasts, which including bone morphogenetic protein 6, runt-related transcription factor 2, and periostin (POSTN) without osteogenic induction; and osterix, collagen type I alpha 2, and POSTN with osteogenic induction. Together, these data indicate that GGCX dermal fibroblasts trans-differentiate into the osteogenic lineage. This study proposes another mechanism underlying aberrant calcification in patients with GGCX syndrome.